Reduction and Sonolysis of Metallic Derivatives

Metallic powders can be prepared from salts or complexes by reduction or decomposition methods, which were reviewed in several articles and papers. These conventional methods exhibit experimental difficulties or provide unsatisfactory results, which encouraged a number of sonochemical investigations. 

The sonochemical reduction of metal halides in the presence of alkali metals, a modification of the Rieke process, applied to a series of metal chlorides, is shown in the general equation 3.58/56 his method, the reduction is carried out with lithium under mild conditions (less than 40 min at room temperature vs several hours with potassium in refluxing THF or DME). The useful low valent (or metallic ) titanium is obtained by sonicating TiCla and lithium at 30°C, instead of reflux in the silent reaction.57 

For salts poorly soluble in THF, the addition of an electron carrier (e.g., naphthalene) is recommended.58/58 

50 Fieser, L.F. Fieser, M. Reagents for Organic Synthesis, Wiley, New York, 1967, Vol. 1, pp. 1292. 

Reactive nickel (Eq. 4), from nickel acetyl-acetonate and sodium, reacts in situ with 1,5-cyclo-octadiene to yield the Ni(COD)2 complexRuthenium chloride is reduced by zinc, and the metal reacts immediately with added ligands 

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